Can jack dempseys live with black ghost knives?

Verdict

Yes, with care

Yes, with care. Jack dempseys and black ghost knives can share a tank, but watch one thing. Jack dempseys are aggressive. Black ghost knives hold their own only in a big tank with places to hide.

Jack Dempsey72–86°F · pH 6.5–7.5

Black ghost knife73–82°F · pH 6–8

What to watch

Watch outJack dempseys are aggressive. Black ghost knives hold their own only in a big tank with places to hide.

What works

Both are fine at 73–82°F.
pH 6.5–7.5 suits both.
They use different parts of the tank: jack dempseys the mid, black ghost knives the bottom.

Water side by side

The green band is the temperature range both can live in.

The green band is the pH both tolerate.

Size to scale

Adult length in an aquarium. A fish can swallow anything that fits in its mouth, roughly a third to half its own length for predators.

Care at a glance

	Jack Dempsey	Black ghost knife
Temperature	72–86 °F	73–82 °F
pH	6.5–7.5	6–8
Adult size	10.0 in	15.0 in
Minimum tank	55 gal	125 gal
Temperament	Aggressive	Semi-aggressive
Swims at	Middle	Bottom
Group	Alone or in pairs	One per tank
Diet	Carnivore	Carnivore

Better tank mates for jack dempseys

CrayfishYes

All jack dempsey tank mates

Better tank mates for black ghost knives

All black ghost knife tank mates

Questions

Can jack dempseys live with black ghost knives?

Yes, with care. Jack dempseys and black ghost knives can share a tank, but watch one thing. Jack dempseys are aggressive. Black ghost knives hold their own only in a big tank with places to hide.

What temperature suits both jack dempseys and black ghost knives?

73–82 °F. Jack dempseys need 72–86 °F, black ghost knives need 73–82 °F.

What size tank do jack dempseys and black ghost knives need together?

At least 125 gal, set by the black ghost knife. Add space for each extra fish.